var i = 1;
function go() {
    var num = parseInt(Math.random()*14+1)+14;
    //生成一个[1,14]之间的随机数，为了确保效果，多转两圈，加28
    var timer = setInterval(function()  {
        num--;
        if (num ==0) {
            clearInterval(timer);
        }
        var items = document.getElementsByClassName('item');
        //var items = $('.item')
        for (var item of items) {
            item.classList.remove('active');
        }
        //设置当前被选中的item，给它添加active class属性
        var item = document.getElementById('item'+i);
        item.classList.add('active');
        i++;
        if(i>14) {
            i = 1;
        }
    }, 100);
}